Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250011 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 711 PM EST MON NOV 24 2014 .SYNOPSIS... LOW PRESSURE INTENSIFYING OVER THE GREAT LAKES WILL BRING AN ASSOCIATED COLD FRONT THROUGH THE MID-ATLANTIC LATE THIS AFTERNOON AND EARLY THIS EVENING. LOW PRESSURE IS EXPECTED TO TRACK NORTH ALONG THE COAST WEDNESDAY. HIGH PRESSURE WILL RETURN FOR THURSDAY AND FRIDAY. && .NEAR TERM /THROUGH TUESDAY/...
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INTERMEDIATE UPDATE...CANCELLED WIND ADZY FOR THE WRN HIGHLANDS AND PERIPHERY ZONES OF THE CURRENT SMALL CRAFT ADZY FOR THE WATERS. FROM PREV DISC...COLD FRONT WILL PUSH EAST ACROSS THE AREA THIS EVENING WITH A WIND SHIFT AND DRYING OF THE AIRMASS. TEMPERATURES WILL BE A BIT SLOWER TO FALL AS THE COLDER AIR IS BLOCKED BY THE MOUNTAINS. LOWS WILL GENERALLY BE IN THE 40S WITH UPPER 30S IN HIGH ELEVATIONS AND LOWER 50S NEAR THE BAY. SOME PATCHY FOG OR STRATUS MAY DEVELOP IN SOUTHERN MD AS THE FRONT SLOWS AND LOW LEVEL MOISTURE POOLS ALONG IT. TUESDAY WILL BE DRY WITH HIGH PRESSURE NOSING IN FROM THE LOWER MISSISSIPPI VALLEY. INCREASING MID AND HIGH LEVEL CLOUDS THROUGH THE DAY AS THE FRONT REMAINS JUST OFFSHORE AND THE LOW PRESSURE SYSTEM BEGINS TO TAKE SHAPE OVER NORTHERN FL. DESPITE BEING MUCH COOLER THAN TODAY... THE COLDEST AIR STAYS POISED OVER THE GREAT LAKES AND HIGHS WILL BE NEAR CLIMO IN THE 50S. SHADED SOUTHEAST CWA A LITTLE COOLER DUE TO THE INCREASING CLOUDS.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
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A POTENT JETMAX/SHORTWAVE WILL TRACK THROUGH THE GULF COAST STATES TUESDAY NIGHT AND THIS WILL CAUSE COASTAL LOW PRESSURE TO DEVELOP OFF THE SOUTHEAST COAST. AT THE SAME TIME...HIGH PRESSURE WILL BUILD TO OUR NORTH ALLOWING FOR COLDER AND DRIER AIR TO FILTER INTO THE REGION. HIGH AND MID-LEVEL CLOUDS WILL INCREASE AHEAD OF THIS SYSTEM TUESDAY NIGHT...BUT MUCH OF THE TIME WILL TURN OUT DRY WITH THE SYSTEM REMAINING TO OUR SOUTH AND WEST. HOWEVER...PRECIPITATION IS EXPECTED TO OVERSPREAD THE AREA QUICKLY EARLY WEDNESDAY MORNING AS THE COASTAL LOW TRACKS NORTHEAST TOWARD CAPE HATTERAS. THE LOW WILL INTENSIFY AS IT TRACKS NORTHEAST...AND THIS WILL ALLOW FOR MOISTURE FROM THE ATLANTIC AND GULF OF MEXICO TO GET WRAPPED INTO THE STORM. THEREFORE...PRECIPITATION WILL BE MODERATE TO LOCALLY HEAVY AT TIMES DURING THE DAY WEDNESDAY. THE MAIN QUESTION IS HOW MUCH COLD AIR WILL WORK ITS WAY INTO THE REGION...CAUSING THE THREAT FOR SNOW. AS OF NOW...IT APPEARS THAT THERE WILL BE ENOUGH COOLING FROM THE WET-BULB EFFECT AND DYNAMICAL COOLING FOR ANY RAIN OR MIXED PRECIPITATION TO QUICKLY CHANGE TO SNOW FOR LOCATIONS NEAR THE MASON-DIXON LINE AND ALSO NEAR AND WEST OF THE BLUE RIDGE MOUNTAINS. THE HEAVIEST SNOW ACCUMULATION IS MOST LIKELY TO FALL IN THE MOUNTAINS...BUT THERE IS A POTENTIAL FOR SEVERAL INCHES OF SNOW ACROSS MOST OF THESE AREAS SO A WATCH HAS BEEN ISSUED. FOR LOCATIONS CLOSER TO INTERSTATE 95...THERE MAY BE ENOUGH WARM AIR FOR PRECIPITATION TO START OUT AS RAIN...BUT EVEN ACROSS THESE AREAS PRECIPITATION WILL LIKELY CHANGE TO SNOW DUE TO THE COOLING AFFECTS PREVIOUSLY MENTIONED. HOWEVER...SURFACE TEMPS WILL HOVER CLOSE TO OR PERHAPS EVEN A COUPLE DEGREES ABOVE FREEZING AND THIS MAY MAKE IT DIFFICULT FOR SNOW TO STICK. THE HIGHEST DEGREE OF UNCERTAINTY IS IN THESE AREAS SO PLEASE STAY TUNED TO THE LATEST FORECASTS FOR UPDATES. FOR LOCATIONS SOUTH AND EAST OF I-95...MOSTLY RAIN IS EXPECTED...BUT THERE IS A POTENTIAL FOR SNOW TO MIX IN WEDNESDAY AFTERNOON. PRECIPITATION WILL END FROM SOUTHWEST TO NORTHEAST LATER WEDNESDAY AFTERNOON INTO WEDNESDAY EVENING. EXACT TIMING IS STILL UNCERTAIN BUT THE FORECAST LEANS A BIT TOWARD THE MORE PROGRESSIVE GUIDANCE SINCE THIS SHOULD BE A FAST MOVING SYSTEM AND IT IS NOT EXPECTED TO PHASE WITH THE NORTHERN BRANCH UNTIL AFTER IT IS OFF TO OUR NORTH. TEMPS WILL DIP BELOW FREEZING WEDNESDAY NIGHT AS CONDITIONS DRY OUT. THEREFORE...ANY WET OR SLUSHY ROADS MAY FREEZE UP.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... LOW PRESSURE DEPARTS INTO THE CANADIAN MARITIMES THURSDAY. MEANWHILE...500 MB NORTHERN STREAM TROUGH MOVES ACROSS THE AREA. SNOW SHOWERS POSSIBLE OVER THE WESTERN RIDGES BUT TRAJECTORIES NOT FAVORABLE FOR PROLONGED UPSLOPE. CANNOT RULE OUT A FEW FLURRIES EAST OF THE RIDGES AS THE TROUGH AXIS PASSES BUT MOSTLY JUST EXPECTING PASSING CLOUDS IN A BREEZY WEST FLOW. HIGHS SHOULD MAKE IT TO AROUND 40 DEGREES THURSDAY AFTERNOON. COLDER TEMPS AT 850 MB ACCOMPANY THE NORTHERN STREAM WAVE...SO BELOW NORMAL TEMPS ARE EXPECTED LATER THIS WEEK. SURFACE HIGH PRESSURE MOVES ACROSS FRIDAY INTO FRIDAY NIGHT...THEN MOVES OFFSHORE FOR THE WEEKEND ACCOMPANIED BY A GRADUAL WARMUP TO NEAR NORMAL TEMPERATURES. A FRONT MAY APPROACH THE AREA BY THE BEGINNING OF NEXT WEEK. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. SOUTHERLY WIND GUST APPROX 25KT WILL CONTINUE THROUGH THIS AFTERNOON...DIMINISHING WITH SUNSET. COLD FRONTAL PASSAGE WILL OCCUR THIS EVENING WITH A WIND SHIFT TO THE SOUTHWEST...WHICH COULD VARY WITHIN A COUPLE HOURS OF WHAT IS CURRENTLY IN THE TAFS. WINDS GRADUALLY BECOME MORE WESTERLY BY LATE TONIGHT. WINDS AROUND 10KT OR LESS THROUGH TUESDAY. VFR CONDITIONS ARE EXPECTED TUESDAY NIGHT. A RAIN AND SNOW MIX WILL OVERSPREAD THE TERMINALS EARLY WEDNESDAY MORNING. PRECIPITATION WILL CHANGE TO ALL SNOW WEDNESDAY AND IFR CONDITIONS ARE EXPECTED. THE LOW WILL MOVE AWAY FROM THE AREA WEDNESDAY NIGHT AND CONDITIONS WILL IMPROVE TO VFR LEVELS. GUSTY NORTH-NORTHWEST WINDS ARE POSSIBLE WEDNESDAY INTO EARLY WEDNESDAY EVENING. MAINLY VFR EXPECTED THU-THU NIGHT W/ W WIND 10-15 KTS. VFR INTO NEXT WEEKEND...WINDS BECOME LIGHT/VARIABLE AS HIGH PRESSURE MOVES OVERHEAD FRI-FRI NIGHT...THEN S AROUND 10 KTS SAT. && .MARINE... STRONG SOUTHERLY WIND GUSTS WILL CONTINUE ON THE WATERS THROUGH THIS AFTERNOON. WINDS WILL SHIFT TO THE SOUTHWEST THIS EVENING WITH A COLD FRONT PASSAGE THEN GRADUALLY DIMINISH WHILE BECOMING WESTERLY. NOT A STRONG SURGE OF COLD AIR...SO GUSTS SHOULD TAPER OFF DESPITE THE FRONTAL PASSAGE. HAVE KEPT THE SMALL CRAFT ADVISORY THE SAME...ENDING AT 8 PM FOR THE MID/UPPER TIDAL POTOMAC AND AT 1 AM FOR THE REST OF THE WATERS. WESTERLY WINDS THROUGH THE DAY TUESDAY AT LESS THAN 15KT. LOW PRESSURE WILL DEVELOP OFF THE SOUTHEAST COAST TUESDAY NIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT LATE TUESDAY NIGHT FOR THE MARYLAND CHESAPEAKE BAY FROM SANDY POINT TO SMITH POINT AND FOR THE LOWER TIDAL POTOMAC RIVER FROM COBB ISLAND TO SMITH POINT. THE LOW WILL MOVE UP THE MID-ATLANTIC COAST WEDNESDAY AND IT WILL INTENSIFY AS IT MOVES OFF TO OUR NORTHEAST WEDNESDAY NIGHT. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR THE WATERS WEDNESDAY INTO WEDNESDAY EVENING. A GALE WARNING MAY BE NEEDED FOR PORTIONS OF THE WATERS WEDNESDAY. GUSTY WEST WINDS BETWEEN DEPARTING/DEEPENING LOW PRESSURE AND APPROACHING HIGH PRESSURE WILL LIKELY BREACH SMALL CRAFT ADVISORY CRITERIA THURSDAY NIGHT INTO FRIDAY. WINDS WILL LIGHTEN AS HIGH PRESSURE MOVES OVERHEAD FRIDAY AFTERNOON AND NIGHT...THEN SOUTHERLY CHANNELING LOOKS TO BRING A RETURN TO HIGHER GUSTS SATURDAY AFTERNOON. && .TIDES/COASTAL FLOODING... A SOUTHERLY FLOW HAS CAUSED TIDAL ANOMALIES TO INCREASE THIS AFTERNOON. HOWEVER...THE ASTRONOMICAL NORMS ARE RELATIVELY LOW. THEREFORE...MINOR COASTAL FLOODING IS NOT EXPECTED WITH THE HIGH TIDE CYCLE THIS EVENING. ANOMALIES WILL DECREASE BEHIND A COLD FRONT LATER TONIGHT. && .CLIMATE...
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HIGH TEMPERATURES TODAY FOR DCA/IAD/BWI WILL ALL COME VERY NEAR CURRENT RECORDS. HERE ARE THE RECORD HIGHS AND THE YEAR THEY OCCURRED... DCA...74 IN 1958. ..OFFICIALLY TIED.. IAD...74 IN 1979. BWI...73 IN 1979.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY AFTERNOON FOR MDZ003>007-501-502. VA...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY AFTERNOON FOR VAZ025>031-036>040-042-501-503-504. WV...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY AFTERNOON FOR WVZ050>053-055-501>506. MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ532>534-537- 540>543. SMALL CRAFT ADVISORY FROM 1 AM TO 6 AM EST WEDNESDAY FOR ANZ532>534-537-540>543.
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&& $$ UPDATE...GMS PREV DISCUSSION...ADS/BJL/DFH

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